1. Field of the Invention
The present invention is generally directed to feedthroughs for implantable medical devices, and more particularly, to a feedthrough having a non-linear conductor.
2. Related Art
There are several types of implantable medical devices (sometimes referred to as “medical implants” herein) that are designed to be temporarily or permanently implanted within a patient or recipient (“recipient” herein). Implantable medical devices may be partially implantable, including both one or more implantable components and one or more external components, or completely implantable. Such implantable medical devices perform one or more of a variety of therapeutic functions such as stimulate nerve or other tissue, monitor biological functions or physiological parameters, transfer materials between the exterior and interior of the recipient, perform functions previously performed by organs or other biological systems, etc.
Depending on the application and/or intended function, an implantable component of a partially or completely implantable medical device can be implanted directly underneath the skin or deep within a recipient adjacent to or in an organ or bone of the recipient. In order to minimize the amount of surgery and/or discomfort to the recipient, it is generally desirable to make implantable components as thin and compact as possible. This is of even greater importance when the recipients are young children.
Cochlear implants use direct electrical stimulation of auditory nerve cells to bypass absent or defective hair cells that normally transduce acoustic vibrations into neural activity. Such devices generally use an electrode array inserted into the scala tympani of the cochlea so that the electrodes can selectively stimulate cells of the recipient's auditory nerve.
Auditory brain stimulators are used to treat a smaller number of recipients with bilateral degeneration of the auditory nerve. For such recipients, the auditory brain stimulator provides stimulation of the cochlear nucleus in the brainstem, typically with a planar electrode array; that is, an electrode array in which the electrode contacts are disposed on a two dimensional surface that can be positioned proximal to the brainstem.
Implantable medical devices, such as those described above, include one or more functional components located within an implantable housing of an implantable component. As used herein, a “functional component” refers to any mechanical, eletro-mechanical, or electronic component of an implantable medical device. Typically, at least some of the functional components, such as electronic components, incorporate non-biocompatible materials (e.g. copper, lead, ferrite, etc.) and thus these components must be located in a hermetic enclosure. This hermetic enclosure protects the body from any non-biocompatible materials contained in an implantable component and protects the electronic assembly from body fluids. A breakdown in the hermetic enclosure can lead to adverse reactions in the recipient (e.g., inflammation or cytotoxicity) or the device (e.g., malfunctions) and necessitate removal of one or more implantable components, or can cause a recipient to stop using the device to avoid the above or other adverse effects.
In certain implantable medical devices, an electrically conductive path is provided through a wall of the hermetic enclosure to allow electrical signals to be communicated between components within the hermetic enclosure and components outside of the hermetic enclosure. For example, in a cochlear implant, electrical stimulation pulses may be provided from within a hermetic enclosure to electrodes disposed outside of the hermetic enclosure that are used to directly stimulate auditory nerve cells. Electrical feedthrough arrangements typically comprise one or more electrically conductive pins mounted in a glass or ceramic insulator to electrically insulate the pin from the container or housing.